Determinação da cinética de cristalização em diferentes escalas visando o projeto de cristalizador em batelada utilizando o sistema monopentaeritritol-água como modelo.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Previous studies on crystallization as an industrial process have been frequently limited to just one aspect of the process. They usually study parameter optimization or a method for monitoring solution or suspension, frequently not taking into account the several aspects that compose the quality of crystalline product, or the fact that the studied process is such more important when can be applied in industry. From this point of view, this study proposes to go forward to the evaluation of feasibility of industrial application of its own results. Initially, it was determined the solubility of the model-system monopentaerythritol in water to infer from this result some thermodynamic parameters, specific heat and heat of crystallization, which are necessary to a possible crystallizer design. Afterwards, it was done the optimization of the crystallization parameters in seeded cooling batch of the model-system, by monitoring suspension tubidity, and refractive index of solution and chord length distribution of the crystals, in three different scales: 0,35 L in reactor of 0,6 L, 1,05 L in reactor of 2L, and 6,2 L in reactor of 9L. In-line monitoring of system properties, as well as the measurement of crystal size distribution and measurements of optical microscopy of seeds and final product, allowed the optimization of kinetic parameters, considering the existence of agglomeration in two of the three studied scales. With the obtained kinetic parameters, the extrapolation of them to other scales was tried. This scale up was not possible, but it was utilized the kinetic parameters obtained in the 9 L reactor to design a crystallization system, considering two crystallizers: one larger of 40 m suitable to product an intermediate chemical as pentaerythritol, and a smaller one of 2 m considering the system as a specialty chemical. The simulations carried out, utilized in the design of the crystallizers, allowed to verify that there is limitation in heat exchange of the larger designed crystallizer which hinders the imposition of non-linear cooling profiles, normally indicated in scientific papers as adequate solution to improve the performance of produced crystals. This limitation does not exist in the smaller designed crystallizer, which allows imposing non-linear cooling profiles and maximizing the performance of crystalline product, by obtaining larger crystals with narrow size distribution.

ASSUNTO(S)

engenharia quimica . cristalização aplicações industriais cristalização descontínua controle de processo pentaeritritol cristalização

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